The present invention relates to high voltage electrical equipment, such as a focused ion beam processing and observation system, to which high voltage is applied to accelerate ions or charged particles.
Electrical equipment with a high voltage portion of 20 [kV] or more, such as a focused ion beam processing and observation system, has a structure in which the vacuum container body and the high voltage power supply are separable to help the maintenance of the body. In such high voltage electrical equipment, the dielectric strength of the electrical connection between the power supply side and the body side is important.
Conventional techniques for improving the dielectric strength include, for example, providing a space in the electrical connection between the power supply side and the body side to increase the creepage distance. As another conventional technique, filling of transformer oil having high dielectric strength into the windings to which high voltage is applied has been proposed for a transformer of the power supply, as described by Japanese Application Patent Laid-Open Publication Nos. Hei 05-190353, Hei 05-299197, and Hei 06-283299.
In the above-described conventional technique that provides a space around the high voltage connection to increase the creepage, keeping the given dielectric strength needs sufficient distance dimension and creepage, which may enlarge the electrical equipment body. In addition, changes in the environment around the electrical equipment may cause condensation or moisture absorption on the high voltage insulation surface. Thus, more leakage current may pass through the insulator to reduce its dielectric strength so that it was difficult to provide compact electrical equipment.
The object of the present invention is to provide reliable electrical equipment which can prevent the leakage current increase due to the condensation or moisture absorption on the high voltage insulation surface and improve the dielectric strength, and can be made compact.
In accordance with one aspect of the present invention, there is provided high voltage electrical equipment including a bushing terminal which connects to an electric wire for supplying high voltage electricity, a connection bushing which holds the bushing terminal, and a flange on a power receiving side in which the connection bushing is detachably fitted and which has a flange terminal to be connected to the bushing terminal, comprising, an insulating liquid sealed in a space between the connection bushing and the flange on the power receiving side, the space being formed when the connection bushing is attached to the flange on the power receiving side.
The insulating liquid is preferably a fluorine-based insulating liquid which has dissolved water of 50 [ppm] or less at 40 [xc2x0 C.].
In accordance with another aspect of the present invention, the high voltage electrical equipment comprises an insulating gas sealed in a space between the connection bushing and the flange on the power receiving side, the space being formed when the connection bushing is attached to the flange on the power receiving side.
The insulating gas is preferably dry nitrogen, dry air, or dry carbon dioxide which has a water content of 300 [ppm] or less with a dew point of xe2x88x9240 [xc2x0 C.], and insulation equal to or higher than that of the air.
In accordance with still another aspect of the present invention, a water repellent treatment including a fluorine-based resin material is applied to a surface of the connection bushing, which the surface faces the space.
Such a configuration can prevent the condensation or moisture absorption on the insulator surface in the space of the high voltage connection, and can prevent the leakage current increase even under high humidity environment, and can provide compact equipment with high dielectric strength.
The high voltage electrical equipment includes an electron source such as an electron microscope, or an ion source, and can apply to and is suited for electronic devices that process and observe samples with accelerated ion beams.